This application is based upon and claims the benefits of priority from the prior Japanese Patent Application Nos. 2000-300987 and 2000-300994 filed on Sep. 29, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to an electric cell using a negative electrode of aluminum.
Currently, manganese cells, alkaline cells, and so on have been used as electric power sources of a wide variety of portable electric devices such as handheld personal computers, personal digital assistants (PDAs), and cellular phones. Typically, each of these cells comprises: a negative electrode made of zinc; and a positive electrode made of manganese, with an electromotive force of 1.5 volts. As the portable electric devices became more advanced, the improvements in high voltage, high capacity, and lightweight characteristics of primary or secondary cells have been demanded.
In contrast, it has been expected that the improvements in high voltage, high capacity, and lightweight characteristics of such primary cells would be easily attained, compared with those of the primary cells using the negative electrodes made of zinc. Thus, the primary cells using negative electrodes made of aluminum have been investigated and developed for a long time. Among the prior art technologies, for example, U.S. Pat. No. 2,838,591 (1958) discloses a primary cell comprising a positive electrode containing manganese dioxide, a negative electrode made of aluminum, and an electrolyte consisting of a weak-acid aqueous solution of aluminum chloride. In this case, however, the aluminum employed in the negative electrode tends to react with the electrolyte, so that there are several problems of generating a gas as a reaction product and increasing the amount of self-discharge. Moreover, it is demanded that a primary cell of a high output by which a larger amount of current can be obtained as compared with that of using a weak-acid aqueous solution of aluminum chloride as an electrolyte.
To overcome the limitations in the prior art described above and other limitations that will become apparent upon reading and understanding the present specification, it is an object of the present invention is to provide an electric cell using aluminum or aluminum alloy in a negative electrode.
In the first aspect of the present invention, an electric cell using aluminum in a negative electrode comprises a positive electrode, the negative electrode containing aluminum or aluminum alloy, and an electrolyte arranged between the positive electrode and the negative electrode, wherein the electrolyte includes: at least one ion selected from a group of a sulfate ion (SO42xe2x88x92) and a nitrate ion (NO3xe2x88x92); and an additive selected from a group of an organic acid, a salt of the organic acid, an hydrate of the organic acid, an ester of the organic acid, an ion of the organic acid, and derivatives thereof.
In a second aspect of the present invention, an electric cell using aluminum in a negative electrode comprises a positive electrode, the negative electrode containing aluminum or aluminum alloy, and an electrolyte arranged between the positive electrode and the negative electrode, wherein the electrolyte comprises at least one ion selected from a group of a sulfate ion (SO42xe2x88x92) and a nitrate ion (NO3xe2x88x92); and a surface of the negative electrode is contacted with one selected from an organic acid, a salt of the organic acid, an hydrate of the organic acid, an ester of the organic acid, an ion of the organic acid, and derivatives thereof.
Here, the additive or a material to be contacted with the surface of the negative electrode can be at least one functional group selected from a carboxylic group (COOH), a sulfonic group (SO3H), a hydroxyl group (OH), and a nitro group (NO2); and a derivative thereof.
The additive or a material existing on the surface can be a polymeric compound and a derivative thereof.
The electrolyte may contain a halogen ion.
In a third aspect of the present invention, an electric cell using aluminum in a negative electrode comprises a positive electrode, the negative electrode containing aluminum or aluminum alloy, and an electrolyte arranged between the positive electrode and the negative electrode, wherein the electrolyte includes at least one ion selected from a group of a sulfate ion (SO42xe2x88x92) and a nitrate ion (NO3xe2x88x92); and the surface of the negative electrode includes an oxide layer containing at least one element selected from a group of chromium, sulfur, nitrogen, boron, carbon, and phosphorus.
Here, the negative electrode may include the oxide layer containing: at least one of organic acid selected from a group of sulfuric acid, nitric acid, oxalic acid, chromic acid, boric acid, phosphoric acid, carbonic acid, sulfosalicylic acid, maleic acid, acetic acid, and carboxylic acid; an ion of the organic acid; a salt of the organic acid; or derivatives thereof.
In a fourth aspect of the present invention, a cell using aluminum in its negative electrode comprises a positive electrode, a negative electrode containing aluminum or aluminum alloy, and an electrolyte arranged between the positive electrode and the negative electrode, wherein the electrolyte includes: at least one ion selected from a group of a sulfate ion (SO42xe2x88x92) and a nitrate ion (NO3xe2x88x92); and an additive, where the additive includes one of: a heterocyclic organic compound containing nitrogen; and a nitrogen-containing organic compound containing at least one functional group selected from a group of an amino group, an imino group, an azi group, and an azide group, an ion of the nitrogen-containing organic compound, a salt of the nitrogen-containing organic compound, or a derivative of the nitrogen-containing organic compound.
Here, the negative electrode may be comprised of an alloy of aluminum with at least one metal selected from Mn, Cr, Sn, Ca, Mg, Pb, Si, In, and Zn.
The thickness of the oxide layer may be from 0.1 nm to 1,000,000 nm, preferably from 5 nm to 50,000 nm.
The amount of the organic acid to be introduced into the oxide layer may satisfy 10xe2x88x9211xe2x89xa6yxe2x89xa60.1, preferably 10xe2x88x927xe2x89xa6yxe2x89xa60.1 when the composition of an oxide coating film is defined as Al2O3+zXy where X denotes Cr, S, N, B, C, or B, and Z is a given number.
The additive may be at least one selected from a group of: methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, phenol, glycerol, glycolic acid, ethylene glycol, formic acid, acetic acid, propionic acid, oxalic acid, salicylic acid, sulfosalicylic acid, malic acid, tartalic acid, succinic acid, fumaric acid, phtalic acid, malonic acid, citric acid, maleic acid, lactic acid, butyric acid, pyruvic acid, benzoic acid, sulfobenzonic acid, nitromethane, sulofoaniline, sulfonyl nitorobenzene, polyvinyl alcohol, vinyl acetate, vinyl sulfonate, poly (sulfonate vinylbenzene), poly(vinyl acetate), methyl acetate, acetic anhydride, maleic anhydride, phthalic anhydride, diethyl malonate, sodium benzoate, sodium sulfobenzoate, sulfoaniline chloride, chlorethyl acetate, dichlormethyl acetate, poly (vinyl acetate potassium salt), poly (stylene lithium sulfonate), polyacrylate, and lithium polyacrylate.
The concentration of the additive in the electrolyte may be from 0.0001 to 40% by weight, preferably from 0.0001 to 30% by weight.
The above and other objects, effects, features, and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.